- Skin cells are among the best potential vehicles for introducing new genes into humans for the purpose of gene therapy for local disease or for systemic metabolic disease. Work to date has established the usefulness of epidermal keratinocytes and fibroblasts for expressing and delivering new genes locally and systemically, but technical and safety issues raise questions about currently employed methods used to introduce new genes into those cells. The goal of this research is to demonstrate the feasibility of using homologous recombination to insert new genes into specific gene loci in epidermal keratinocytes and fibroblasts. This method should provide predictable, durable, and relatively safe expression of new genes. The specific aims of this project are I) to insert a marker gene, the bacterial enzyme lacZ, into the beta-actin locus of cultured human keratinocytes and fibroblasts or into the keratin 5 locus of keratinocytes and II) to select clones of targeted cells and to evaluate the duration of lacZ expression in vitro and in vivo, following transplantation of the targeted cells into athymic mice.